Recently, lithium secondary batteries have received the most attention due to their characteristics of high energy density and long lifetime. In general, a lithium secondary battery includes an anode formed of a carbon material or a lithium metal alloy, a cathode formed of lithium metal oxide, and an electrolyte in which a lithium salt is dissolved in an organic solvent.
Lithium has been initially used as an anode active material constituting the anode of the lithium secondary battery. However, since lithium may have low reversibility and safety, a carbon material has currently been mainly used as the anode active material of the lithium secondary battery. Although the carbon material may have a lower capacity than lithium, the carbon material may have smaller volume changes as well as excellent reversibility and may also be advantageous in terms of cost.
Recently, the demand for high-capacity lithium secondary batteries has gradually increased as the use of the lithium secondary battery has expanded. As a result, a high-capacity electrode active material replaceable with a low-capacity carbon material has been required. For this, research into using a (semi) metal, such as silicon (Si) and tin (Sn), which exhibits a higher charge and discharge capacity than a carbon material and is electrochemically alloyable with lithium, as an electrode active material has been undertaken.
In a case where the (semi) metal electrochemically alloyable with lithium, such as silicon, is used, cracks or fine particles may be generated due to the changes in volume caused by repeated charge and discharge of a battery, and thus, the battery may degrade. As a result, capacity of the battery may decrease. Also, there has been a case in which oxide of the (semi) metal was typically used as an electrode active material in order to reduce the cracks or fine particles due to the changes in volume. However, in this case, since lithium oxide or lithium metal oxide, as an irreversible phase caused by an initial reaction with lithium ions, is formed, an initial efficiency of the battery may decrease.